PTO shaft material: How much weight will it support?

[krazykevin76]

I'm creating an additional step for my tractor. It currently has two steps and I want to make a third step closer to the ground. I've bought an linear actuator that will lower and raise the step. I didn't want a lot of play in the step so instead of going the square tubing route, I went with PTO shaft material. I'll weld the outer shaft to a piece of plate and bolt that to my existing step outer rails. I will then bolt my new step to the inner PTO shaft material. The actuator will allow the step to go down and hit a stop. So the actuator wont' be holding any weight, just the PTO shaft material and my existing step. The material I bought has these dimensions: Inner tube has 4mm thick walls and is 36.1mm height, so basically the diameter. This material is basically a triangle with rounded corners. The outer tube has 3.3mm wall thickness and the height/diameter is 43.4mm. I'll put a link so you guys can see the shape.

https://www.agrisupply.com/outer-tubing-series-4/p/102584/

I've been thinking to myself if one tube per side would be enough or should I go ahead and plan on doubling it up. The length of inner tube being used will only be about 10in or so and my outer wall material that I will use for the guide will probably be 3 or 4 inches which will be welded to a piece of 1/4" plate and bolted to the existing tractor step side rail. Again, all this fancy PTO route was to make a nice telescoping step with no play. Maybe a tad over thinking, but I want to try this route and see if it works. If I went with just one support on each side of the step, how much weight would it safely handle?

Thank you


Kevin

 

[Gutman]

how much weight would it safely handle?

Depends.

PTO shafts are designed with torsional loads in mind, but from your link and some googfoo on pto shafts, it looks like your choice of material is roughly 10ga tubing (not quite sure of grade, astm500 or better?). Should be adequate for the task from a materials perspective.

My gut says it'd carry the load, but my vision of what you're looking to do may not match yours; the devil is always in the details. A pic or sketch would sure help me.

I'm envisioning an intended setup (3-4 inches of outer tube as a guide or sleeve on each siderail of the existing steps and 10 inches of inner tube for the step to allow 6-7 inches of travel).

But: Intended load? Length of step? Incline angle of existing steps, if any? Weld method and joint type? Attachment method for step? Etc.

I've been thinking to myself if one tube per side would be enough or should I go ahead and plan on doubling it up.

Not sure what you're thinking here when you're referring to tube and doubling up.

I'm confident something could be done, but unless the ground clearance issue is important, I think a fixed step is much easier and less complicated.

 

[larry_g]

Sounds way over complicated to me. The time you do hit it it will be much more of a repair than something simple that is made to break away.

lg

 

[whateg01]

Not sure I understand but in my head I have pictured an L with the PTO shaft being the vertical section and the step obviously being the horizontal. If you are stepping close to the vertical shaft, that will help. But a lot depends on how far out the shaft extends. If it's only a foot, it'll do better than if you had 3 feet. (I know you won't have a 3' step, but it illustrates the point better.)

 

[krazykevin76]

I know the image is way clearer in my head and I apologize, but whateg01 has it. It's not complicated at all. It's for a John Deere tractor and it is just to extend down from the bottom step. Most tractors have two or 3 steps already built on them. They are not made to break away. They have to support the weight of a person climbing on them. I need this extra step about 8" closer to the ground than the current step. If you leave the step down it will not last more than a day in use. The "L" shape is correct. The PTO material will be the vertical pieces and the step will be horizontal as the other steps are. Retracted, my new step will be flush with the bottom of the existing lowest step. Click a button and the step will lower 8" for an addition step. Very simple design but I was just wanting to make sure the material I had in mind would support us big guys. Whateg01 is correct again in that it will only travel 8" so this won't be a 3ft stick, very short and compact.

Gutman: By doubling up I meant instead of having just one inner/outer combo on each side supporting vertically, I would use two on each side.

Kevin